State law requiring a 100-year water supply before new residential development may proceed ensures sustainable growth in Arizona's major metropolitan areas and protects Arizona's citizens.

Preserving the unseen groundwater under Arizona's deserts for use in times of drought is essential for our state's prosperity. For many decades, Arizona lawmakers were unable to agree on ways to limit groundwater pumping, resulting in falling water tables, land subsidence and costly lawsuits. Threats by the federal government to suspend funding for construction of the Central Arizona Project finally spurred the state into action. In 1980, Arizona embarked on a remarkable journey to manage its groundwater supplies with the passage of the Groundwater Management Act. Hailed as one of the nation's ten most innovative programs in state and local government by the Ford Foundation and the John F. Kennedy School of Government, the goal of the Act is to eliminate the overuse of groundwater in the state's most heavily populated areas, known as Active Management Areas or AMAs. In AMAs, the Act mandates water conservation, regulates who may withdraw groundwater and how much, limits well drilling, and requires the demonstration of a 100-year assured water supply for all new residential subdivisions. It continues to be one of the most progressive laws in the country for managing groundwater.

The assured water supply requirement has been perhaps the most successful tool to curb groundwater pumping, because it requires most new development to be served with renewable water supplies, such as surface water. Recognizing, however, that not all landowners and water providers have access to renewable supplies, state law was amended in 1993 to give the Central Arizona Water Conservation District (CAWCD)--the entity that operates the Central Arizona Project--the responsibility of helping these landowners and water providers to obtain an assured water supply, even though they would be pumping groundwater. This responsibility of the CAWCD has become known as the Central Arizona Groundwater Replenishment District, or CAGRD.

Here's how it works. If a water provider or a developer wishes to rely on groundwater to demonstrate an assured water supply, it must become a member of CAGRD. As a member of CAGRD, the landowner or provider pays CAGRD incrementally to replenish -- store renewable supplies underground -- any groundwater pumped by the member that exceeds the limitations imposed by the state's Assured Water Supply Rules.

The membership of CAGRD has expanded far more quickly than many anticipated in 1993. CAGRD staff currently project that CAGRD's replenishment obligation for current members could reach 136,500 acre-feet annually by 2035. An acre-foot is enough water to serve approximately 2.5 households for a year. To meet this obligation, CAGRD will need to acquire annual rights to another 125,000 acre-feet of renewable water supplies. To date, CAGRD has collected only a small amount of the revenue needed to secure these water rights. The rest will have to be collected over time through significant rates and fees charged to CAGRD members. As developers subdivide and sell land, the burden falls on individual homeowners to pay these rates and fees.

This situation has led the CAWCD Board of Directors to conclude that the risk to CAGRD associated with enrollment of new members must be mitigated. CAWCD and water users are currently discussing conditions on enrollment, including whether new members should be required to pay for replenishment supplies up-front. AMWUA supports the efforts to reform how CAGRD enrolls new members in the future. This reform is necessary to continue sustainable development, while safe-guarding Arizona's water supplies for future generations. Stay tuned.